Hello,
i was going for a sail today, ran across no wind, and decided to motor a bit more into the chesapeake to see if we culd get some wind a bit further from land. well, as i did this the wife informed me that there was smoke below. I cut out the engine, went down to investigate, and realized it was exhaust and the engine compartment was flooded with it. So, we both sat outside, and motored in spewing exhaust everywhere, but we got back in. I opened the hachs, placed a few fans around to help, and once I could breathe below, I dove in.

As far as I could tell, the exhaust flange on the engine manifold goes up and back down and has a pipe out of the top of the loop that goes back into the heat exchanger. after this T fitting, is where my problem was, the pipe that then connects this to the exhaust hose, that goes into a black round thing before it goes overboard. Well ,after the t fitting the pipe that the exhaust connects too was corroded away at the threads. it filled the boat with exhaust and warm water. the fitting was wrapped in an insulator and a fiberglass(i presume?) which was soaked through and very black. So, to a few questions, what is this thing that corroded away? I thought it was an exhaust elbow, but i am not sure if its an exhaust riser. should i replace the corroded piece or the whole thing and what should i replace it with? I don't want to spend 5k on titanium, which I saw was the thing to use to prevent this from ever happening as i dug around online to understand how screwed I am. I saw one guy who was using brass here actually. Also, the black stuff, is that exhaust only? or it is oil as well? and what is the black round thing? thanks for all the help

I believe that the corroded fitting is where the raw cooling water is injected into the exhaust, cooling it and providing water for the waterlift muffler (the "black round thing"). The black should just be the exhaust and the water is the raw water from the heat exchanger (if you have one) or the engine block (if you are raw water cooled). The elbow that the fitting goes into is usually cast metal and difficult, though not impossible, to tap with new threads. look to see if the threads in the elbow are ok, if they are you just need a new fitting. If the're corroded you could try to drill out the corrosion and retap; or spring for a new elbow.

There should not be any oil there at all. Diesel exhaust is pretty dirty stuff, good luck cleaning it up!

where the cooling water connects to the exhaust is the mixing elbow. you're better off getting a new mixing elbow. beside corrosion & leak of the joint, its likely you have fouling and particle blockage of the elbow, leading to the muffler. with new assembly your engine will breathe better.

Hello, thank you for all the advice. I noticed something else when i was working on it yesterday, the exhaust riser has a copper tube that comes down from the inlet nipple from the water inlet. Is that standard? Also, I have been looking around and is there a problem with building a new system myself? I found a reducing Tee at plumbing fittings direct that would replace the old elbow. Is this a bad idea? Looking at it, it doesnít seem to be any different, the exhaust still comes in from the top, and I could get a spare to have handy when it corrodes again. This does raise one issue, what should the fittings be made of? Will galvanized pipe be enough, or should I go with stainless or brass? I have read stainless is bad, but is commonly used as long s welds can be avoided, or done properly. I have only heard of a guy redoing his A4 system using brass, and some people just say to use the black pipe and replace it every 4-5 years. I only plan on using the motor sparingly, I have a sailboat, not a motorboat and I like my quiet. Any advice would be appreciated.

I would recommend getting a manufactured exhaust elbow for the A4. After 3 rebuilds of A4's I went diesel but the original exhaust (dry jacket) weighed too much and corroded, the hand built galvanized elbow wrapped in heatshield disintegrated within the wrap from raw salt water cooling, and after replacing that with the manufactured elbow and anti siphon set up the galvanized joint between the manifold and elbow fractured after being attached to the diesel.
If you're running raw water the best setup will probably last 5 years if you don't asphyxiate yourself with CO before it rusts through.
The advantage of the precast elbows is that the cooling water come in over the top of the elbow so it is cool on top ( where it usually is below the underside of the cockpit sole) and obviates the need for the heat wrap that can hide a leak.
Thank goodness when the galvanized section fractured I was towed to a yard that honestly assessed the problem as a $5.00 pipe joint that could be removed from the manifold with a pipe wrench and didn't require a new manifold end.I suggest a fresh water system and the less metal in the exhaust the better.

OldColumbia, I have a univesal 25XP, do you still recommend an A4 elbow? I was planning on replacing the setup I described earlier once every three years, at roughly $50 a pop, it's a minimal cost and from what I gather that is about the expected life cycle of any setup(4-5 years). also, the same thing happend to me, the nipple that caried the dexhaust/raw water to the pipe corroded away and that is where my leak started. I do not quite understand how having the cooling come from atop means yuou don't have a heat wrap, do you mean only on the seawater side? thanks for the help, i apprecaite it.

I apologize, since I misread that you had an Atomic 4. I replaced my last Atomic 4 with a remanufactured Universal 25XP (because I could, based on the footprint) and the riser elbow/anti-syphon system that had been installed after A4 rebulid number two (except for the galvanized nipple between the manifold and riser/elbow) works fine.
Since the 25XP is freshwater cooled you shouldn't have the corrosion inherent with salt water and heat that ate my former wrapped "homemade" riser. The manufactured elbow cost about $130 and I bought brass fittings threaded to hose bib for the connection to the exhaust hose to the Vetus water pot muffler/back flow preventer. Likewise, brass fittings were used for the water injection port.
Since the water injection portion of the elbow is molded above and around the hot gas section, the only "hot" section is the nipple between the manifold and the elbow approximately 2" between threaded ends.
Because my engine is just at or below the water line, anti siphon breaks are important to keep from "sucking water" into the block by excessive cranking that can fill the pot muffler. It's better to close the seacock and reopen when the engine starts than ruin an engine that tries to compress water.
Hope this helps.

oldcolumbia, thank you for all the help, this does't make sense then, or I am not understanding how this works. I had accidentally left my bilge pump off when the exhaust piece finally decided to break off, so the bottom of my boat was covered in warm water that had escaped out of the exhaust. i did not taste it, and it was black too, but there was so much of it, it had to be seawater, and I just traced the hose to the saltwater intake as well. looking at my manual, I see it is a freshwater system, but I am pretty sure its seawater from the heat exchanger that is flowing into the exhaust, and overboard from the water lift muffler, not the engine coolant. also, this prompted me to look more thoroughly at the waterlift muffler, it has no water outlet, is this right? does the exhaust and the water all exit through the exhaust hose? I am thoroughly confused now. where do you get the manufactured elbow? again thanks

oldcolumbia, thank you for all the help, this does't make sense then, or I am not understanding how this works. I had accidentally left my bilge pump off when the exhaust piece finally decided to break off, so the bottom of my boat was covered in warm water that had escaped out of the exhaust. i did not taste it, and it was black too, but there was so much of it, it had to be seawater, and I just traced the hose to the saltwater intake as well. looking at my manual, I see it is a freshwater system, but I am pretty sure its seawater from the heat exchanger that is flowing into the exhaust, and overboard from the water lift muffler, not the engine coolant. also, this prompted me to look more thoroughly at the waterlift muffler, it has no water outlet, is this right? does the exhaust and the water all exit through the exhaust hose? I am thoroughly confused now. where do you get the manufactured elbow? again thanks

regards,
jhack82
s/v Firefly

Yes, it's salt water. All engines inject water into the exhaust system just after it exits the engine to cool the exhaust. The waterlift muffler just adds a place where the water collects temporarily to provide a muffling effect so that your exhaust isn't too loud. That water is then blown out of the boat exhaust along with all the exhaust gasses.

One of the things you need to get into the habit of doing is checking the exhaust a few seconds after you start the engine to assure that water is in fact coming out of the exhaust. That assures you that the cooling system is working before you harm something by running too long without it.

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